The assassination of President John F. Kennedy is a national tragedy mired in myth, captivating Americans even decades after the case was closed. But as authors and historians continue to ponder the players involved in the plot to kill Kennedy, one CIA expert is insisting on a much-debated Cuban connection.

Retired CIA analyst Brian Latell contends in his new book, Castro’s Secrets: The CIA and Cuba’s Intelligence Machine, that the former Cuban president was well aware of Kennedy assassin Lee Harvey Oswald’s intention of killing the American leader.

The Miami Heralddetails Latell’s vast examination of Castro’s intelligence operations, which includes interviews with Cuban defectors and spies, as well as declassified documents from the FBI, CIA and the Pentagon. In what the Herald calls “potentially explosive” claims, Castro’s Secrets recounts a story of a frustrated Oswald leaving the Cuban embassy in Mexico City after failing to acquire a visa just months before the Dallas murder. After visa rejections from both Cuba and the Soviet Union, the Castro supporter allegedly vowed to kill Kennedy, and forewarned DGI (Dirección General de Inteligencia) Cuban intelligence officers of his plans.

“Everything I write is backed up by documents and on-the-record sources,” Latell told the Herald. “There’s virtually no speculation.”

According to Latell, some of that evidence includes reports of a defector instructed to drop radio surveillance of the CIA just hours before the assassination to focus on any signals out of Texas. CIA wiretaps from the Cuban embassy in Mexico City revealed conversations that Latell interprets to mean embassy officials knew a wealth of information about the incident before little was reported. Luisa Calderon, a 20-something English-speaking DGI officer, was recorded only four hours after the assassination as saying she knew about it “almost before Kennedy did.”

The book also alleges that one of Cuba’s top ranking officials, who was recruited by CIA agents to assassinate Castro, was in fact acting as a double agent. Latell claims that Rolando Cubela fed American intelligence to assassinate Castro directly to the leader himself. “He wanted definitive proof that Kennedy was trying to kill him,” Latell said. “And he got it.” Though Cubela was arrested in 1966 and sentenced to life in prison for plotting to murder Castro, Latell believes it was merely a ruse to mask his double agency.